...It takes care of setting the correct order of options as these can become very long with multiple pages where you have page and TOC options for each page. It makes usage in server-type applications easier, every instance (PDF process) has its own output buffer which contains the PDF output and you can feed one input document from an io.Reader (using stdin in wkhtmltopdf). You can combine any number of external HTML documents (HTTP(S) links) with at most one HTML document from stdin and set options for each input document.